Encontrado mais um Big Bang da vida tipo folhelho de Burgess

segunda-feira, agosto 30, 2010

A new Burgess Shale–type assemblage from the “thin” Stephen Formation of the southern Canadian Rockies

Jean-Bernard Caron1, Robert R. Gaines2, M. Gabriela Mángano3, Michael Streng4 and 
Allison C. Daley4

-Author Affiliations

1Department of Natural History-Palaeobiology, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario M5S 2C6, Canada
2Pomona College, Geology Department, 185 E. Sixth Street, Claremont, California 91711, USA
3Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
4Department of Earth Sciences, Uppsala University, Villavägen 16, 75236 Uppsala, Sweden

The famous Phyllopod Beds of the Walcott Quarry. Image from The Burgess Shale Geoscience Foundation


A new Burgess Shale–type assemblage, from the Stephen Formation of the southern Canadian Rocky Mountains, is described herein. It occurs near Stanley Glacier in Kootenay National Park, 40 km southeast of the type area near Field, British Columbia. While at least a dozen Burgess Shale localities are known from the “thick” Stephen Formation, the Stanley Glacier locality represents the first discovery of Burgess Shale–type fossils from the “thin” Stephen Formation. The Cathedral Escarpment, an important regional paleotopographic feature, has been considered important to the paleoecologic setting and the preservation of the Burgess Shale biota. However, the Stanley Glacier assemblage was preserved in a distal ramp setting in a region where no evidence of an escarpment is present. The low-diversity assemblage contains eight new soft-bodied taxa, including the anomalocaridid Stanleycaris hirpex n. gen., n. sp. (new genus, new species). Nektonic or nektobenthic predators represent the most diverse group, whereas in relative abundance, the assemblage is dominated by typical Cambrian shelly benthic taxa. The low diversity of both the benthic taxa and the ichnofauna, which includes diminutive trace fossils associated with carapaces of soft-bodied arthropods, suggests a paleoenvironment with restrictive conditions. The Stanley Glacier assemblage expands the temporal and geographic range of the Burgess Shale biota in the southern Canadian Rockies, and suggests that Burgess Shale–type assemblages may be common in the “thin” Stephen Formation, which is regionally widespread.

Received 31 January 2010.
Revision received 9 April 2010.
Accepted 14 April 2010.
© 2010 Geological Society of America